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5.3L LS Small Block Build - Modern Mouse, Part 7

Turbocharged Boost!

By Richard Holdener, Photography by The Author
Sucp 1206 000 3L Ls Small Block Build Part 7

From day one, the idea behind Modern Mouse was to subject the 5.3L LS to all manner of testing, including everything from bolts-ons to blowers. Nitrous, a stroker upgrade, and even old-school carburetion helped round out the battery of tests, but the LM7 (now stroked to 383 cubic inches) emerged not only unscathed, but begging for more.

Subjecting Modern Mouse to all this abuse helped demonstrate the gains offered by various modifications. This in turn helps readers make informed decisions about which route to take when it comes time to modify their own ride. The impressive power output offered by the stock and modified 5.3L also makes a compelling case for choosing the little LM7 for your Chevy-powered hot rod in the first place. You might think that after six different installments, we would run out of things to test, but we have just scratched the surface. This month, we decided to introduce not just Modern Mouse, but a pair of LM7s to turbocharging. Confused? Read on!

Test 1 Single Turbo: Stock 5.3L LM7

Though Modern Mouse was currently sporting no less than 383 cubic inches, we decided to take a step back and illustrate the gains offered by turbocharging to two different 5.3L combinations. We were lucky enough to secure a second stock LM7 to run our first test this month. We figured running both stock and modified combinations would help our readers--after all, not everyone is going to build a duplicate of Modern Mouse.

The stock 5.3L was purchased from a local wrecking yard at an exceptional price, but we soon found out why. The LM7 take-out was advertised as complete, but was actually missing the throttle body and exhaust manifolds. It also had a cracked oil pan.

We cured this situation with an Accufab throttle body and a Moroso F-body pan we had from a previous test. The stock motor was run with a set of QTP long-tube headers and an electric water pump. For the single turbo, we got a set of JBA shorty headers. Tuning was provided by a FAST XFI/XIM management system and a set of 36-psi injectors. Run in stock trim (after optimized tuning), the 5.3L produced 361 hp at 5,400 rpm and 386 lb-ft of torque at 4,600 rpm. Torque production exceeded 350 lb-ft from 3,200 rpm to 5.400 rpm.

The 5.3L was then subjected to boost from a single turbo kit from HP Performance. The kit was designed for a Chevy truck, but it illustrated the potential of boosting a stock 5.3L perfectly. The kit included a dedicated Y-pipe that hooked directly to the stock exhaust manifolds (or our shorty headers). Though available with different turbos, we chose a 67-mm T4 HPQ turbo from Precision Turbo. It was capable of supporting nearly 800 hp on the right application, so it had no trouble on this otherwise stock 5.3L.

The kit from HP was available with and without an intercooler, and we elected to try it both ways. Run on pump gas at just under 8 psi in non-intercooled form (with a safe tune), the turbocharged 5.3L produced 510 hp at 5,400 rpm and 521 lb-ft of torque at 4,700 rpm. Adding the intercooler allowed us to increase the boost pressure to 11.3 psi, where the turbo 5.3L pumped out 608 hp at 5,700 rpm and 641 lb-ft of torque at 4,700 rpm.

Test 2-Twin Turbo-- Modern Mouse

Unlike the stock 5.3L, we built a custom twin turbo system for Modern Mouse. Though custom, the system illustrated what is possible with properly- sized turbos on an already powerful normally aspirated LM7 combination. The twin turbo system featured a pair of 76-mm turbos combined with a twin-core, air-to-water intercooler that featured dual 3-inch inlets and a single 3.5-inch outlet all from CX Racing.

  • Sucp 1206 003 3L Ls Small Block Build Part 7
    1 Before putting boost to Modern Mouse, we decided to illustrate what turbocharging can do to a stock 5.3L. The new boneyard 5.3L was first run normally aspirated to establish a baseline. Running long-tube headers and an Accufab throttle body, the LM7 produced 361 hp and 386 lb-ft of torque.
    Sucp 1206 003 3L Ls Small Block Build Part 7
    1 Before putting boost to Modern Mouse, we decided to illustrate what turbocharging can d
  • Sucp 1206 004 3L Ls Small Block Build Part 7
    2 Don't count out the stock truck intake for turbocharging, as the impressive torque production helps spool up the turbo.
    Sucp 1206 004 3L Ls Small Block Build Part 7
    2 Don't count out the stock truck intake for turbocharging, as the impressive torque prod
  • Sucp 1206 005 3L Ls Small Block Build Part 7
    3 The turbo kit from HP Performance was first run in low-boost mode without an intercooler. Running 7.8 psi of boost, the turbo 5.3L produced 510 hp and 521 lb-ft of torque. The Ford MAF was used as a reducer to attach the 3-inch discharge tubing to the Accufab throttle body.
    Sucp 1206 005 3L Ls Small Block Build Part 7
    3 The turbo kit from HP Performance was first run in low-boost mode without an intercoole
  • Sucp 1206 006 3L Ls Small Block Build Part 7
    4 Adding the intercooler allowed us to increase the boost pressure to 11.3 psi. This increase in boost pushed the power output of the stock 5.3L to 608 hp and 641 lb-ft of torque. Not too shabby for a junkyard mill.
    Sucp 1206 006 3L Ls Small Block Build Part 7
    4 Adding the intercooler allowed us to increase the boost pressure to 11.3 psi. This incr
  • Sucp 1206 007 3L Ls Small Block Build Part 7
    5 After running the single turbo on the stock 5.3L, we turned our attention back to Modern Mouse, You will remember from previous installments that Modern Mouse was now sporting 383 cubic inches.
    Sucp 1206 007 3L Ls Small Block Build Part 7
    5 After running the single turbo on the stock 5.3L, we turned our attention back to Moder
  • Sucp 1206 008 3L Ls Small Block Build Part 7
    6 The 383 stroker was plenty stout thanks to a set of forged pistons from Probe Racing, a set of Fel Pro head gaskets, and ARP head studs.
    Sucp 1206 008 3L Ls Small Block Build Part 7
    6 The 383 stroker was plenty stout thanks to a set of forged pistons from Probe Racing, a
  • Sucp 1206 010 3L Ls Small Block Build Part 7
    7 Back in part four, we swapped out the milder grind for a Comp hydraulic roller cam. The healthy Comp cam offered a .617/.624 lift split, a 231/239-degree duration split and 113-degree LSA.
    Sucp 1206 010 3L Ls Small Block Build Part 7
    7 Back in part four, we swapped out the milder grind for a Comp hydraulic roller cam. The
  • Sucp 1206 011 3L Ls Small Block Build Part 7
    8 For our turbo test, we installed a set of CNC-ported LS1 heads from Procomp Electronics. The 220cc intake ports flowed over 320 cfm.
    Sucp 1206 011 3L Ls Small Block Build Part 7
    8 For our turbo test, we installed a set of CNC-ported LS1 heads from Procomp Electronics
  • Sucp 1206 012 3L Ls Small Block Build Part 7
    9 The CNC work on the LS1 heads from Procomp Electronics included the combustion chambers. A portion of the impressive flow figures can be attributed to the 2.055/1.60 valve package.
    Sucp 1206 012 3L Ls Small Block Build Part 7
    9 The CNC work on the LS1 heads from Procomp Electronics included the combustion chambers
By Richard Holdener
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